Hi there, I was playing around with my DVD driver properties the other day and I found a DVD region tab. Have a look in it, see if it helps you with your problem.
Rightclick your DVD drive and click properties. Under the hardware tab is a button properties, make sure the DVD drive is highlighted and click it. From there you should see the tab DVD region.
It says To play a regionalised DVD on your computer, you must set the DVD drive to play disks from that region. I have never had a problems with this myself, but give it a try.